Regular and Chaotic Motion in Globular Clusters

As a first step towards a comprehensive investigation of stellar motions within globular clusters, we present here the results of a study of stellar orbits in a mildly triaxial globular cluster that follows a circular orbit inside a galaxy. The stellar orbits were classified using the frequency analysis code of Carpintero and Aguilar and, as a check, the Liapunov characteristic exponents were also computed in some cases. The orbit families were obtained using different start spaces. Chaotic orbits turn out to be very common and while, as could be expected, they are particularly abundant in the outer parts of the cluster, they are still significant in the innermost regions. Their relevance for the structure of the cluster is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The sediment budget and dynamics of a delta‐canyon‐lobe system over the Anthropocene timescale: The Rhone River delta,Lake Geneva (Switzerland/France)

Deltas are important coastal sediment accumulation zones in both marine and lacustrine settings. However, currents derived from tides, waves or rivers can transfer that sediment into distal, deep environments, connecting terrestrial and deep marine depozones. The sediment transfer system of the Rhone River in Lake Geneva is composed of a sublacustrine delta, a deeply incised canyon and a distal lobe, which resembles, at a smaller scale, deep‐sea fan systems fed by high discharge rivers. From the comparison of two bathymetric datasets, collected in 1891 and 2014, a sediment budget was calculated for eastern Lake Geneva, based on which sediment distribution patterns were defined. During the past 125 years, sediment deposition occurred mostly in three high sedimentation rate areas: the proximal delta front, the canyon‐levée system and the distal lobe. Mean sedimentation rates in these areas vary from 0·0246 m year^?1 (distal lobe) to 0·0737 m year^?1 (delta front). Although the delta front–levées–distal lobe complex only comprises 17·0% of the analysed area, it stored 74·9% of the total deposited sediment. Results show that 52·5% of the total sediment stored in this complex was transported toward distal locations through the sublacustrine canyon. Namely, the canyon–levée complex stored 15·9% of the total sediment, while 36·6% was deposited in the distal lobe. The results thus show that in deltaic systems where density currents can occur regularly, a significant proportion of riverine sediment input may be transferred to the canyon‐lobe systems leading to important distal sediment accumulation zones.     

已知e或a的先验值的初轨迭代算法

本文讨论由短弧测角资料,已知偏心率ｅ 或半长轴ａ 的先验值时,初轨的迭代算法。某根数的先验值可看作是对该根数的具有一定精度的观测量,在加权残差平方和达到极小意义下,本文导出了最小二乘估计的迭代算法。仿真结果显示,周期的估计精度主要取决于偏心率先验值的精度;当ｅ 足够小时,可用园轨道计算的ａ′作为ａ 的先验值,定出的初轨有较高精度。     

Comparative biomonitors of coastal trace metal contamination in tropical South America (N. Brazil)

Samples of 5 bivalve molluscs (Crassostrea rhizophorae, Mytella charruana, Anomalocardia brasiliana, Anadara ovalis, Phacoides pectinata), 2 barnacles (Fistulobalanus citerosum, Balanus amphitrite) and leaves of the mangrove tree Rhizophora mangle were collected from up to 11 sites in two estuaries in Natal, Brazil--the comparatively contaminated Potengi estuary and the comparatively uncontaminated Curimataú estuary. Specimens were analysed for the trace metals Zn, Cu, Cd, Fe, Mn and Ni, and a comparative assessment made of the power of the different species as trace metal biomonitors. Four of the 5 bivalves (not P. pectinata) take up metals from solution and suspended material (food source), while P. pectinata as a lucinid with symbiotic chemosynthetic bacteria takes up metals from dissolved sources only. The organisms with the strongest net accumulation of particular metals showed the greatest discrimination between trace metal bioavailabilities between sites. Barnacles (F. citerosum) showed the best discrimination, but oysters (C. rhizophorae) are particularly recommended as biomonitors given their strong accumulation patterns for many trace metals, their large size and their local abundance.     

Angular dislocation of the earth principal axes of inertia

The coefficientsC ₂₁ andS ₂₁ are usually considered to be zero in theory (e.g. the axis of earth rotation was used as the principal axis of inertia). However, satellite measurements show thatC ₂₁ as well asS ₂₁ are non-zero, indicating that the axis of rotation of the earth is not the principal axis of inertia. This work determines the angles by which the principal axes of inertia must be rotated in relation to the geocentric coordinate system (where theZ axis coincides with the rotating axis of the earth).     

Case study and numerical simulation of the summer regional circulation in São Paulo,Brazil

The three-dimensional mesoscale circulation in the vicinity of the city of São Paulo is examined through model simulations validated by observational data obtained during a field experiment. The complex terrain surrounding the plateau where the city is located, plus proximity to the sea, represent the local controls on the wind field with implications for boundary-layer transport of atmospheric constitutents. The coupling of a regional-scale circulation with slope and sea-breeze circulations is an important feature which determines the wind regime in São Paulo in a summer situation not influenced by frontal systems.     

Earthquake loss assessment of precast RC industrial structures in Tuscany (Italy)

A seismic loss assessment for structural, non-structural, contents and business interruption is presented for precast reinforced concrete industrial buildings located in Italy. The correlation that exists between the performances of such spatially distributed buildings (i.e. spatial correlation) given a seismic event should be considered when estimating losses at a local or regional level. Loss assessment is thus performed herein using the OpenQuake-engine, an open-source tool capable of including the spatial correlation of ground-motion residuals and uncertainty in building vulnerability. The annual probability of structural collapse is employed as an initial risk measure, in which each industrial facility is considered as an individual asset. Then the economic loss for 300 buildings in the province of Arezzo is computed using a probabilistic event-based risk approach and presented in terms of annual average losses and losses at given annual rates of exceedance. The impact of the losses due to business interruption is also explored, and the extent of customer base is used as a prioritization metric for risk mitigation. It is observed that risk reduction should be applied as a priority in the facilities that are compromising the current level of acceptable risk, and the results show that business interruption has a significant contribution for economic losses, whose repercussions go beyond the regional level. Although this application is confined to the province of Arezzo, the same methodology can be used in other regions in Italy with similar building stock.     

Comparing directional line sets using non-parametric statistics: a new approach for geoenvironmental applications

The need to compare the distributions of directions of the discontinuities present in rock masses prompted the development of a new surrogate measure for non-parametric statistical tests. This is used to quantify the degree of matching between polymodal azimuth direction distributions determined from remotely sensed data for different areas and also between these and field measurements. The approach is based on an application of the Kolmogorov–Smirnov (K–S) goodness-of-fit test. However, in this application the main interest is to accept the null hypothesis (instead of rejecting it) so that there is a risk of committing a Type II statistical error when it is false, particularly if sample sizes are too small. Therefore, a method that employs a set of empirical criteria for calibrating the statistical decision was devised. The statistic used (D _ratio) provides a measure of the degree of reliability about the decision on whether or not to accept or reject the hypothesis. The methodology is tested and implemented using existing geological data and a tectonic model valid over a limited region, within which two study areas were taken for these developments. The results obtained indicate reasonable improvement of the performance of K–S tests for inferential purposes when empirical reliability criteria are used. This was acknowledged by increased matching between occurring and inferred discontinuities (tectonic structures) and reduction in rates of errors. Other applications envisaged include different data sources such as climate and soil data.     

Allochthonous subsidies of organic matter across a lake–river–fjord landscape in the Chilean Patagonia: Implications for marine zooplankton in inner fjord areas

Ecosystems can act as both sources and sinks of allochthonous nutrients and organic matter. In this sense, fjord ecosystems are a typical interface and buffer zone between freshwater systems, glaciated continents, and the coastal ocean. In order to evaluate the potential sources and composition of organic matter across fjord ecosystems, we characterized particulate organic matter along a lake–river–fjord corridor in the Chilean Patagonia using stable isotope (δ¹³C) and lipid (fatty acid composition) biomarker analyses. Furthermore, estimates of zooplankton carbon ingestion rates and measurements of δ¹³C and δ¹⁵N in zooplankton (copepods) were used to evaluate the implications of allochthonous subsidies for copepods inhabiting inner fjord areas. Our results showed that riverine freshwater flows contributed an important amount of dissolved silicon but, scarce nitrate and phosphate to the brackish surface layer of the fjord ecosystem. Isotopic signatures of particulate organic matter from lakes and rivers were distinct from their counterparts in oceanic influenced stations. Terrestrial allochthonous sources could support around 68–86% of the particulate organic carbon in the river plume and glacier melting areas, whereas fatty acid concentrations were maximal in the surface waters of the Pascua and Baker river plumes. Estimates of carbon ingestion rates and δ¹³C in copepods from the river plume areas indicated that terrestrial carbon could account for a significant percentage of the copepod body carbon (20–50%) during periods of food limitation. Particulate organic matter from the Pascua River showed a greater allochthonous contribution of terrigenous/vascular plant sources. Rivers may provide fjord ecosystems with allochthonous contributions from different sources because of the distinct vegetation coverage and land use along each river’s watershed. These observations have significant implications for the management of local riverine areas in the context of any human project that may modify terrestrial habitats as well as the productivity, food webs, and community structure of rivers, lakes, fjords, and the coastal ocean in the Chilean Patagonia.     

Millennial/submillennial-scale sea-level fluctuations in western Mediterranean during the second highstand of MIS 5e

This paper investigates a series of small-scale, short-lived fluctuations of sea level registered in a prograding barrier spit that grew during the MIS 5e. This interglacial includes three highstands (Zazo et al., 2003) and we focus on the second highstand, of assumed duration ～10 ± 2 ka, given that U–Th ages do not provide more accurate data. Geometry and 3D architecture of beach facies, and thin-section petrography were used to investigate eight exposed offlapping subunits separated by seven conspicuous erosion surfaces, all interpreted as the result of repeated small-scale fluctuations of sea level.Each subunit records a relatively rapid rise of sea level that generated a gravelly shoreface with algal bioherms and a sandy uppermost shoreface and foreshore where most sand accumulated. A second range of still smaller-scaled oscillations of sea level has been deduced in this phase of sea-level fluctuation from lateral and vertical shifts of the foreshore-plunge-step-uppermost shoreface facies.Eventually, progradation with gently falling sea level took place and foreshore deposits underwent successive vadose cementation and subaerial dissolution, owing to relatively prolonged exposure. Later recovery of sea level re-established the highstand with sea level at approximately the same elevation, and there began deposition of a new subunit. The minimum sea-level variation (fall and subsequent rise) required to generate the observed features is 4 m. The time span available for the whole succession of events, and comparison with the Holocene prograding beach ridge complex in the nearby Roquetas (Almería) were used to calculate the periodicity of events. A millennial-suborbital time scale is suggested for fluctuations separating subunits and a decadal scale for the minor oscillations inside each subunit.